Spinal fusion is a known technique to correct spinal injuries, deformities, and/or degenerative conditions. Lumbar fusion, for example, is generally an open procedure. An open procedure includes making a relatively large surgical incision to access the surgical site. A surgeon may implant a fusion cage into an intervertebral disc space. Next, the surgeon immobilizes the adjacent vertebral bodies using fixation rods attached to the superior and inferior vertebral body. Immobilizing the superior and inferior vertebral body allows bone to grow and fuse the superior and inferior bodies into one mass of bone.
As can be appreciated, the open procedure described above results in a relatively significant amount of trauma to the patient as a significant amount of tissue and muscle must be cut and retracted to allow access to the surgical site. Minimally invasive tools and procedures have been developed to reduce the amount of trauma as well as reduce the recovery time. One such minimally invasive system includes the '110 patent disclosed above. The '110 patent allows for a smaller or minimal incision by providing a surgical corridor formed by inner and outer sleeves that locked to a pedicle screw or a pedicle screw tulip. A surgeon accesses the surgical site through the surgical corridor formed by the sleeves.
Another minimally invasive tool is disclosed by U.S. Pat. No. 7,951,175, titled INSTRUMENTS AND METHODS FOR MANIPULATING A VERTEBRA, issued May 31, 2011, and incorporated herein by reference as if set out in full. The '175 patent similarly describes a tool that forms a corridor and connects to a bone anchor. The '175 patent has a proximal end extending from the patient. The inner sleeve of the instrument is movable relatively to the outer sleeve, via a plunger or the like, that resides along the center line of the corridor formed by the tool. The instrument 10 disclosed by the '175 patent provides for a minimally invasive mechanism to manipulate the vertebrae and to seat the rods 90A, 90B into the bone anchors, but does not provide a convenient mechanism to move the rods 90A, 90B from outside the patient to inside the patient.
Other similarly minimally invasive tools provide a special rod introduction tool. For example, United States Published Patent Application Publication Number 2012/0253402A1, filed Jun. 14, 2012, titled PEDICLE SCREW EXTENSION FOR USE IN PERCUTANEOUS SPINAL FUSION, the disclosure of which is incorporated herein as if set out in full, provides for a rod introducer that slidingly engages the outside of a pedicle screw extension and moves a rod into position as the tool slides from a proximal to a distal location along the extension. The tool of the '340 application, as well as other similar pedicle screw extenders as they are generally know in the art, leaves much to be desired. In particular, rod introducers for the current extenders are customer tools that are adapted to engage the outside of the extender, rather than using the hollow center of the extenders. The rod introducer is offset from the pedicle screw extender requiring a slightly larger incision. Also, the pedicle screw extenders themselves, as presently constructed, provide an obstructed view of the surgical area.
Thus, against the above background, an improved pedicle screw extender would be desirable.